First-principles calculations of the hydrogen adsorption mechanisms of Na-Mt

Shale primarily consists of clay minerals, and underground hydrogen storage projects leverage the superior adsorption properties of these minerals to store significant amounts of hydrogen, addressing the growing need for large-scale energy storage. Consequently, investigating the hydrogen adsorption mechanisms in sodium montmorillonite (Na-Mt) has become a key area of focus in new energy research. This study employs density functional theory (DFT) calculations to assess the hydrogen adsorption energy between Na-Mt layers, comparing the density of states, elastic constants, and storage capacity before and after adsorption. The results show that as hydrogen adsorption increases in the interlayer region of Na-Mt, both the adsorption energy and weight density of Na-Mt rise. Additionally, the total density of states increases with adsorption, peaking at the top of the valence band. During the adsorption process, the volume of montmorillonite increases linearly in the c-axis direction, while the a- and b-axis directions do not change much. Hydrogen adsorption reduces the stiffness of montmorillonite in the c-axis direction, and the overall mechanical properties of sodium montmorillonite are all decreased during the adsorption process. The theoretical work in this paper not only helps to understand the process of hydrogen adsorption on montmorillonite, but also provides new ideas for hydrogen storage.